This invention relates to a device for positioning an endotracheal tube in the trachea with respect to the carina, and more particularly regards a positioning device with a carina-engaging stop consisting of three flexible extensions which form a tripodal configuration.
Intubation of the the trachea with a double-lumen catheter for the purpose of selective ventilation of the lung is known in the art. For example, a double-lumen tube, illustrated in FIG. 1, is inserted into the trachea 10 for selective inflation of the lungs through the left and right bronchi 12 and 14, respectively. The double-lumen tube 16 includes a left bronchial tube 18, a tracheal tube 20, a bronchial cuff 22, and a tracheal cuff 24. The bronchial cuff is mounted on the left bronchial tube near the tube's distal end 25. The tracheal cuff surrounds both the bronchial and tracheal tubes near the distal end 26 of the tracheal tube. The left bronchial tube is slightly curved near its distal end 25.
The double-lumen tube 16 is used by inserting the two distal ends 25 and 26 into the trachea 10 with the distal curvature of the bronchial tube 22 to the left and parallel to the surface supporting the patient. The tube is inserted until the bronchial cuff 22 enters the left bronchus 12. At this point, the tube 16 is properly positioned and the cuffs 22 and 24 are inflated. Now, either lung individually or both lungs together can be inflated through the distal ends 25 and 26 of the tube 16.
In order for the endotracheal tube 16 to be correctly operated, it must be precisely positioned so that the tracheal cuff 24 is not inserted so far down into the trachea as to seal off the right main bronchus, thereby preventing inflation of the right lung. Further, if the tube 16 is not inserted far enough, the bronchial cuff 22, when inflated, can distend over the carina 13 into the right bronchus, thereby providing an imperfect seal of the left bronchus and partially occluding the right bronchus.
Practitioners skilled in the art of using double-lumen endotracheal tubes know that the correct operation of a double-lumen tube will be assured if the cuffs 22 and 24 are correctly positioned with regard to the carina 13. In this regard, the tracheal cuff 24 must be positioned cefelad or proximal to the bronchial bifurcation marked by the carina 13, while the bronchial cuff 22 must be positioned within the left bronchus, downwardly displaced in the bronchus with respect to the carina 13.
Conventionally, correct positioning of an endotracheal tube in the trachea is done with respect to the carina 13, which provides a clearly distinguishable reference point in the tracheal complex. Positioning of the tube and assessment of lung inflation is typically accomplished with bilateral ausculation of the chest with a stethoscope during unilateral ventilation. This method is notoriously difficult and inaccurate for reliably determining the tube's position. Positioning can also be assessed by the aid of an X-ray apparatus. However, the limitations of an X-ray apparatus are well known. Such apparatus is large and static and does not always provide the resolution necessary for precise positioning. Fiber optic endoscopes are also used for positioning endotracheal tubes. However, such devices are expensive, fragile, and require the use of a trained expert for their operation.
Another means for positioning an endotracheal tube is disclosed in U.S. Pat. No. 4,449,522 of Baum. The Baum positioning device consists of a flexible probe having a pair of foldable arms at its distal end which are folded outwardly from the end of the device when it is inserted through an endotracheal tube initially positioned in the trachea. The outward folding of the device arms is effected by an actuating wire which extends through the device to its near end where it can be operated by a user. When operated by a user, the actuating device unfolds the pair of arms into a V-shaped structure which engages the carina when the positioning device is slid further forward through the endotracheal tube. The positioning device of the Baum patent has certain drawbacks. First, the device is complex and relatively expensive to manufacture, requiring a manually-operated actuating mechanism as an essential part. Next, the carina-engaging portion of the device consists specifically of two arms. It will be evident to the skilled practitioner that if the span of the V-shaped structure formed when the two arms are unfolded is not substantially perpendicular to or does not lie across the carina, the carina might not be engaged and the distal end of the device can track down one bronchus or the other. Third, the arms are foldable, which means that their combined length when each is rotated to the 90.degree. position with respect to the trachea must be less than the diameter of the trachea. Since the arms are further unfolded through that 90.degree. position into a forwardly-angled position to engage the carina, the diameter described by the span of the arms is obviously less than the diameter of the trachea. Thus, in the actuated position, the arms can miss the carina and fit into a bronchus. Further, the actuating force for the arms is directed inwardly, so the design precludes the arms "tracking down" the wall of the trachea to engage the carina. When this device is in the folded position, it requires the folded arms to assume a streamlined profile in order to fit alongside the main element and yet fit within the endotracheal tube. This profile precludes placing rounded, slightly bulbous tips on the arms to prevent penetration of and damage to the tracheal wall. Additionally, each arm must be rotated through an angle of substantially greater than 90.degree. in a direction posing a risk of trauma to the interior surface of the trachea.
Therefore, in view of the conventional means for positioning an endotracheal tube, it is evident that there is a need for an inexpensive, easily-operated device which accurately, reliably and safely positions an endotracheal tube.